Arthroscopic surgery includes the carrying out of various procedures involving joints, such as the knee, the wrist, or the ankle joint. During these procedures, it is necessary to separate or to distract the joint so that access to articular surfaces may be had. Access to the articular surfaces is required both to visualize the procedure through an arthroscope and to carry out procedures such as, for example, debriding. Distraction of a joint creates a space between adjacent articulated bone surfaces. Distraction of the ankle joint, in particular, creates a space between the tibia and the talus, and also the talus and calcaneus.
In the past, one method of ankle joint distraction was accomplished by placing a pair of threaded external fixation pins into the tibia and the talus. The fixation pins were placed by being driven medially or laterally into, but not completely through, the bones. The fixation pins were forced apart by a jack screw, the pins being retained in opposite ends of the screw. The forcing apart of the fixation pins distracted the tibial-talar joint from the medial or lateral side of the ankle.
In this method of distraction, the external fixation pins were placed parallel to one another (perpendicular to the axis of the leg). Forcing apart of the pins by the jack screw caused the pins to deviate from the parallel by pivoting to form an angle.
Another method of ankle joint distraction was similar to that just described, but with the difference that the distal external fixation pin was not placed parallel to the proximal pin, but at a downwardly inclining angle. Forcing the pins apart with a jack screw eventually resulted in the pins becoming parallel when the joint was distracted.
Both of these techniques suffer from the disadvantage that the distraction is performed from one side only, in this case, the medial or lateral side. Performing the distraction from one side does not create a uniform gap between the articulated surfaces. The one-sided procedure causes the bones to pivot somewhat with the result that the spacing on the opposite side will be quite small compared to that on the distracted side. This means that the flow of arthroscopic cleansing fluid will be restricted on the lateral side resulting in less effective flushing of debris and bacteria, and less access to the overall joint.
Both of these techniques suffer from the further disadvantage that the external fixation pins pass through the cortex and end in the cancellous part of the bone. When pressure is applied to the pins, the pins in turn apply pressure only to one thickness of the cortex and therefore tend to pivot and crush the soft and spongy cancellous. In attempts to alleviate the application of excessive pressure with concomitant cancellous damage, and to avoid pin breakage, various springs and strain gauges have been employed with the jack screws.
It would be advantageous therefore to provide an arthroscopic ankle joint distractor and a method of distracting an ankle joint that obviates the problems associated with prior art distractors and methods of spreading ankle joints employing these distractors.